1-alpha-acetylmethadol (LAAM) is a long-acting drug similar to methadone. LAAM has been used to help patients discontinue the use of illegal opiates such as heroin. The body converts LAAM to a metabolic product, designated norLAAM, that is then further converted to dinorLAAM. Both norLAAM and dinorLAAM have greater pharmacologic effects than the parent compound, LAAM. A specific enzyme in the liver called cytochrome P450 3A4 is responsible for both of these conversions. P450 3A4 interacts with a number of drugs that are frequently used in clinical medicine. Ketoconazole, a drug widely used to treat fungal infections, is an example of an agent that inhibits the metabolism of many drugs that are converted by P450 3A4. This study was designed to test the hypothesis that ketoconazole would inhibit the conversion of LAAM, and that LAAM, therefore, would not act as potently. To test this hypothesis, volunteer subjects were given LAAM in one experimental session and then, in a separate session, given LAAM plus ketoconazole. Measurements of conversion of LAAM to its metabolites and measurements of its opiate-like effect were made.